Choice of an OS for a home ZFS NAS

I am preparing a home NAS with an old Athlon 64 X2 3800+, 4 GB ECC RAM, Asus M2V MX motherboard, and a single 3 TB WDC Green (another one as mirror may be installed in the future). It's the cheapest solution I found that includes ECC memory and the higher energy consumption is offset by the lower (zero) cost of acquisition.

The system will be used for:

• music storage and stream to other desktop computers;
• storage of the scanned dia slides (3-4k slides, 180 MB TIFF each one plus reduced quality JPEG version);
• stream of these photos to a local iPad 2 (maybe Plex App? not yet sure);
• (one additional) remote backup via rsync/ssh or ZFS send/receive.

It will be controlled via remote ssh, maybe VNC, no monitor attached. Absolute requirement is a reliable ZFS solution, plus the ability to easily install packets/software/virtual machines and to update remotely (I will be the admin and I don't live near the NAS).

I have mainly three options:

• NAS4free/FreeNAS
• OpenIndiana
• Solaris Express 11 (yeah yeah I know the license requirements, I will write a perl script on it to count it as development machine).

Problems: NAS4free/FreeNAS (I tested only NAS4free) required embedded installation for remote upgrading, but full install for easy addition of software packets. Since I need at least AirVideo Server (linux/win) and Plex App (win/linux) to stream the photos and some videos to iPad (they both require virtualbox), but I cannot be there to install updates, NAS4free/FreeNAS are excluded.
http://www.nas4free.org/general_information.html explains the issue: embedded can be remotely updated, full cannot.
Solaris has also another advantage: Crashplan client supports Solaris and I'm already using it for other backups. I would like to leave the option open, even if I will be doing backups probably through zfs send/receive.
NexentaStor was left out because zfs send/receive are not included in the free version.

The question is now Solaris 11 Express over OpenIndiana. To ease the management, I will be using http://www.napp-it.org

Which one would you suggest and why? I found lots of informations and it's difficult for me to decide. I think (from the napp-it manual) that Solaris has some additional options for SMB shares, but are they really needed at home? I think I won't even use ACLs, since normal unix-style permissions are enough.
OpenIndiana has maybe more frequent updates (Solaris offers only security updates between releases), but again, do I need them? I don't think so. Moreover, this is a NAS that has to work and nothing else, I cannot risk having problems that require me to access the server. Isn't OpenIndiana a bit more… cutting edge (in the Solaris world)? I'm just asking, no need to focus on this for the answer 🙂

I would limit myself to these two options (SE11.1/OI) also because I will be making a NAS for me in the future (where high performances with Mac shares are also required) and Solaris has kernel support for AFP. I will use this server to gather experience as well.

After this long question, thanks in advance! If you need additional info, let me know and I will update this post.

UPDATES
Given the first answers, I will strongly suggest the person paying the hardware to insert a second HD. Better 2x2TB than 1x3TB (3 TB is oversized anyway). I was trying to keep the initial costs down to spread them over a longer period, but better having something good from the beginning.